P. Larry Nelson wrote:
> 
> I apologize to the list but don't understand why, if I changed the subject,
> it would be part of a previous thread.

The header has a in-reply-to field, and a references field. They are 
used for the threading.

> I always thought threads keyed
> off the subject line,

That would be much too simple.

> and I've been using email since it was invented
> back in the 70's.
> 
> Oh well - learn something new every day....

Keep it like that ;)

Matthias

> 
> Thanks!
> - Larry